First-principles investigation of Ge doping effects on the structural, electronic and magnetic properties in antiperovskite Mn(3)CuN.

We have investigated the structural, electronic, and magnetic properties of Mn(3)Cu(1 - x)Ge(x)N (x = 0, 0.125, 0.25) using first-principles density-functional theory within the generalized gradient approximation (GGA) + U schemes. The crystal structure of the compounds is a tetragonal crystal for x = 0 while it is a cubic crystal for x = 0.125, 0.25. The unit cell volume increases as the Ge doping increases. Our GGA + U calculations give a metallic ground state from x = 0 to 0.25 in agreement with experiments. The magnetic structure for x = 0 is found to be the ferromagnetic state while for x = 0.125, 0.25 it is the Γ(5g)-type antiferromagnetic state. From the density of states (DOS), the coupling between Ge 4p and Mn 3d is the main reason for magnetic transition in Mn(3)Cu(1 - x)Ge(x)N.